The movement away from rearwheel drive has meant that a lot of young mechanics are unfamiliar with tasks that a previous generation would have undertaken without giving things another thought.
Stripping front wheel bearings and repacking them with grease is a good example of the sort of task that seldom needs to be done today. Frontwheel driven cars usually have sealed bearings that do not need servicing.
They usually last the life of the car, and if they fail their replacement is time-consuming, but adjustment or repacking is not required.
Kortjan Nothnagel has been a thatcher ever since he left school, and his team of expert roofmakers is known far and wide. He likes to tackle anything that needs doing rather than turn to a professional.
Some time ago he cleaned and repacked the front wheel bearings on his Isuzu one-ton pickup, but soon afterwards he noticed that the front wheels were running very hot. He first felt the heat on his legs as he walked past the bakkie, and then discovered he couldn’t touch the wheels.
Kortjan suspected binding brakes so he parked the vehicle on an incline and released the handbrake.
It immediately started to roll forward, so he knew there must be some other reason. He came to us with the complete background story, which is more than we normally get to hear.
Hennie took the job card from me with the smile of a man who knew exactly what the problem was and he said: “I think old Kortjan put too much grease into the bearing housings.” A strip confirmed this diagnosis, but Japie looked puzzled.
“How can too much grease cause overheating?” Hennie explained: “The rotation of the rollers in the bearing cage churns up the grease, causing the grease to heat up. The air cavity in the bearing housing normally conducts away this heat.
If there is too much grease the bearing has to churn-up too many grease particles with the result that even more heat is released.
This extra heat cannot be conducted away through the air, as usual, because the extra grease has displaced the air. The result is overheating, and the eventual failure of the bearings.”
Hennie then decided to let Japie repack the bearings properly, under his supervision. He told Japie that the amount of grease in the bearing housing should not exceed about 40 per cent of the total volume.
When Kortjan turned up to take delivery of his bakkie he had the air of a man who had learned an important lesson.
